Strongly correlated oxides have been the subject of intense study for the last two decades. Many of these materials exhibit exciting and technically useful properties; examples include high temperature superconductivity, colossal magnetoresistance, ferromagnetism and ferroelectricity. Perovskite ruthenates (Sr,Ca)n+1RunO3n+1 have become a focus in this field, since they exhibit a rich variety of fascinating ordered ground states, such as spin-triplet superconductivity, itinerant magnetism, field-tuned nematic phase, orbital ordering and Mott insulator behavior. The close proximity of these exotic states testifies to the delicate balance among the charge, spin, lattice and orbital degrees of freedom in ruthenates, and provides a remarkable opportunity for observing novel quantum phenomena through controlling external stimuli. In this talk, I will first give a brief overview of research in this area, and then discuss our progress in studies of these materials. Our research focuses on single crystal and thin film growth and characterization of various ruthenates. We have established a complete phase diagram of magnetic and electronic properties of (Sr1-xCax)3Ru2O7, in which we discovered a novel quantum phase with slow dynamics near a quantum phase transition. We have also studied Ti doping effect on Ca3Ru2O7. We find that Ca3Ru2O7 can be tuned from the quasi-2D metal with ferromagnetic bilayers to the Mott-insulating state with the G-type, nearest-neighbor antiferromagnetic order as Ti concentration is increased above 5%. In the Ca2-xSrxRuO4 thin film, we observed a transition from a Mott insulating state to an itinerant ferromagnetic state tuned by the epitaxial strain. I will discuss the mechanism for these emergent phenomena.
Zhiqiang Mao is a professor from the Department of Physics, Tulane University, USA. He graduated from Nanjing Normal University with a BS degree in 1997, and obtained a PhD degree in Physics at University of Science and Technology of China (USTC) in 1992. He joined the USTC faculty in 1992 and was promoted a Research Fellow in 1995. He worked as a postdoc scholar at Kyoto University in 1997-1999 and the Pennsylvania State University in 2000-2002. He joined Tulane faculty since 2002 and was promoted to a tenured full professor in 2009. He chaired the Tulane Physics Department between 2011 and 2014.
Prof.Mao’s research focuses on strongly correlated materials and unconventional superconductors. He has published 236 papers in these areas in peer-reviewed journals. The total citation counts of his published papers exceed 5500, with H-index=37. He has been recognized with several prestigious awards, including the second Prize of Young Scientists sponsored by Chinese Academy of Sciences (1995), the “Jie-Chu-Qin-Nian-Ji-Jin” award (type-A, Chinese NSF, 1996), the “Qiu Shi” award (1997), the Tulane University Presidential Early Career Development Award (2005), the Cottrell Scholar Award (2005), the US NSF CAREER award (2007). He has been named as an endowed professor (Nicholas J. Altiero Professor in Physics) since 2011 at Tulane University, the Changjiang Lectureship Chair Professor at Nanjing University in 2009-2012.
Host: Ying Liu (yingl@sjtu.edu.cn)
Contact: Honglei Zhuang (hlzh@sjtu.edu.cn)